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Posted: 9/12/2020 1:51:34 PM EDT
[Last Edit: mc556][Edited]
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Is there any general rule of thumb? In the event I can’t find some standard large rifle here soon I’ll need to turn to my stash of magnum primers.. Primarily with 4570. jacketed H4198 and hard cast with both trailboss and H4198. Starline Brass I’m not one that likes to deviate from standard load date but would like to hear opinions. |
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Originally Posted By mc556: Is there any general rule of thumb? In the event I can't find some standard large rifle here soon I'll need to turn to my stash of magnum primers. In the event I can't find some standard large rifle here soon I'll need to turn to my stash of magnum primers. Primarily with 4570 jacketed and hard cast with both trailboss and 4198. I'm not one that likes to deviate from standard load date but would like to hear opinions. Begin loading at start load and work up watching for pressure signs. |
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I did some testing a few weeks ago for a coworker who bought lots of SPM primers since that's all they had locally. My loader was set up for 9x19 with 124 and Titegroup with a standard SP primer. When I was done with my loads I immediately loaded 10 rounds with SPM and 10 with SR primers and chronoed them alongside my SP loads. No difference at all. YMMV of course but we've been loading high powered 9mm (way past SAAMI) with the SR primers for about 20 years to stop breechface erosion. Most primer manufacturers will tell you that their SPM and SR primers are identical in cup thickness, alloy, and compound brisance. |
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Originally Posted By opnblstr: I did some testing a few weeks ago for a coworker who bought lots of SPM primers since that's all they had locally. My loader was set up for 9x19 with 124 and Titegroup with a standard SP primer. When I was done with my loads I immediately loaded 10 rounds with SPM and 10 with SR primers and chronoed them alongside my SP loads. No difference at all. YMMV of course but we've been loading high powered 9mm (way past SAAMI) with the SR primers for about 20 years to stop breechface erosion. Most primer manufacturers will tell you that their SPM and SR primers are identical in cup thickness, alloy, and compound brisance. This doesn't surprise me at all. I suspect you may see a difference in group sizing but I don't know. |
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Originally Posted By JamPo: The old rule of thumb is drop a grain and work from there. The only open info I have seen on primer difference is cup thickness. Maybe not a full grain in pistol loads, I would not go below the min charge even if using the magnum primers. |
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I once saw a little speed increase when using Blue-Dot, which is a slow powder that usually don't fully burn in 9mm. it was only a few fps, not much. For a faster more typical powder, I doubt it matters much. You can drop to minimum load and work your way up; but if you wanted to hedge that and split the difference, I doubt you'll have any problems. If these are using typical powder and aren't full-pressure loads, in the end, I bet you don't find any meaningful differences. |
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Originally Posted By JamPo: The old rule of thumb is drop a grain and work from there. The only open info I have seen on primer difference is cup thickness. This. With big and small rifle, I generally find i need .7 to .8 grains less powder with magnum primers to achieve the same velocity. I dont load much for pistol so wont comment on that. |
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Started reloading for .303 British tonight. As to not dip into my currently irreplaceable LR primer stash, I picked up a couple sleeves of Federal 215 LR magnum primers since if they work, I can buy several thousand without issue. Started my load work ups about 1.5 gr lower than I would if I had been using standard primers. Started near the bottom of the load data and ended up 1.3 gr shy of max load. Hopefully gonna try em out this weekend. Shooting for 2450 ish FPS to match the MK7 ammo used by the Brits. |
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Originally Posted By mechtaco04: Started reloading for .303 British tonight. As to not dip into my currently irreplaceable LR primer stash, I picked up a couple sleeves of Federal 215 LR magnum primers since if they work, I can buy several thousand without issue. Started my load work ups about 1.5 gr lower than I would if I had been using standard primers. Started near the bottom of the load data and ended up 1.3 gr shy of max load. Hopefully gonna try em out this weekend. Shooting for 2450 ish FPS to match the MK7 ammo used by the Brits. Why not load to max? I would rather pull down a few rounds than to find out I didn't go high enough while at the range and have to go back again with a handful of rounds. Yes, I've had to do that and why I bring it up...  I now always have cases charged above max in a ladder so I'm covered, well knowing I'll likely have to pull them down. |
| I'm loading large magnum primers in 45/70. I have two loads, my mild load, 16gr unique under a 340 cast PC bullet. and 43gr 4895 under a 405 cast PC bullet. No issues. I tend to load a little under max anyway. |
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